well there is always your "canned" tunes such as Hypertech, Superchips, etc...that sell a programmer with generic tunes. These tunes are written for increasing performance in a STOCK vehicle. Custom tunes using Troyer, SCT, etc are written specifically for your needs and desires and consider all mods already installed to give you more bang for your buck. As you add more mods you can have your tune adjusted to take advantage of any changes made. Because you are relying on a person to make the adjustments in Air / Fuel ratios and things it comes down to expertise. While this is more expensive and time consuming, it yields the best results.